The present invention generally relates to recovering data and more specifically to restoring and/or validating digitally signed data.
The use of the Internet for both business and personal communications has grown dramatically over the past few years, especially in the area of E-commerce. This large increase in message traffic along with the increased complexity of hardware and software, has increased the chance of losing data. Many systems today provide for back-up, as the number of computer crashes is rising.
While there are many conventional data recovery methods, the problem arises for the user in that how does she know if the information recovered has been tampered with? Especially when there have been several well publicized accounts of computer break-ins. One conventional technique to detect if there has been tampering to a message, and hence to the recovered message, is a digital signature. The US government has established a standard for digital signatures, which is given in Federal Information Processing Standards Publications (FIPS PUB) 186, which is incorporated by reference in its entirety.
FIG. 1 illustrates a conventional digital signature technique. The sender of a Message (M) 110 has a Signature Generation Unit 112. The receiver of the message 110 has a Signature Verification Unit 114. The Signature Generation Unit 112 takes message 110 and performs a secure hash 116 on M 110 to produce H(M) 118. H(M) 118 and Private Key 120 are inputted into Digital Signature Algorithm (DSA) Sign 122 to produce a digital signature for H(M) 118, i.e., Sign(H(M)) 124. M 110 and Sign(H(M)) 124 are sent from Signature Generation Unit 112 at a user sender to Signature Verification Unit 114 at a user receiver. M 110 at Signature Verification Unit 114 is then hashed 130 to produce H(M) 132. The secure hash 130 is the same function as secure hash 116. H(M) 132 and Sign(H(M)) 124 are inputted into DSA Verify 136 along with Public Key 131 to validate the message content. A “no” result means the message 110 has been tampered with, while a “yes” result indicates, but does not insure, no tampering. In addition the digital signature authenticates the message, i.e., it assures the recipient that the message is from the source that the message claims to be from.
However, the digital signature relies on a known algorithm that assumes that is very difficult but not impossible to crack. This assumption is becoming weaker and weaker with the rapid increase in computer power. In addition the digital signature assumes that the private key is secret. If the private key is compromised, the security is lost in present, as well as, recovered data. Thus there needs to be better techniques to validate recovered data.